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Re: output unique lines only

by EdwardG (Vicar)
on Dec 06, 2005 at 16:44 UTC ( #514541=note: print w/replies, xml ) Need Help??

in reply to output unique lines only

Here's one approach -

  • Use STDIN and STDOUT for input and output
  • Use a regex to extract the first 'column'. You could also use split, but since you care only about the first column it may be overkill.
  • Use a hash to gather unique filenames

Put it all together and you will have something like this:

# use strict; # helps prevent silly mistakes use warnings; # helpful when writing code while (<>) { # Reads from STDIN if (/^(\w+)\t/) { # If the line starts with one or more 'word' char +acters followed by a tab... my $filename = $1; # ...assume we've got a filename captured $uniq_fnames{$filename} = 1; # ...and add it to our hash. } } print $_,"\n" for keys %uniq_fnames; # prints to STDOUT, can be piped + to a file

Then you could use this as follows

perl < my_non_unique_list_of_files > my_unique_list_of_fi +les


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[marto]: I'd be interested in seeing the schema and some test data. I think the move could be done in stages.
[ambrus]: Corion: did you as the gods release any official opinion about how perlmonks is now on HTTPS?
[Corion]: Discipulus: I think once we have a test environment again and move to git, contribution and change gets easier
[Corion]: ambrus: I think there was some discussion and maybe even an entry in Tidings, but I'm not really sure
[marto]: Back later, got to get the kids ready
[ambrus]: Also, I still have the suspicion that Perlmonks as a website is still horribly insecure, and that a malicious attacker could take over anyone's account easily, and I should tell the details of why I think this in some Cabal-only place.
[Corion]: But the site now is on https (only), and now also with one unified SSL certificate for all PM hoss
[ambrus]: This worries me a lot especially because as a cbstream maintainer, if this happens, I could get falsely blamed for any insecurity.
[ambrus]: Cbstream itself is also insecure because I abandonned it for too long, and it's really ripe for a full rewrite or something now.
[ambrus]: But that's a totally different issue.

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